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Condensation of ethyl thioxamate (II) with bromomethyl D-ribo-1,2,3,4-tetraacetoxybutyl ketone (I) or bromomethyl 2,3,5-tri-O-benzoyl-β-D-ribofuranosyl ketone (IX) afforded ethyl 5-(D-ribo-1,2,3,4-tetraacetoxybutyl)-1,3-thiazole-2-carboxylate (III) and ethyl 5-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-1,3-thiazole-2-carboxylate (X), respectively. Removal of the protecting groups and ammonolysis of the ester gave the respective 5-(D-ribo-1,2,3,4-tetrahydroxybutyl)-1,3-thiazole-2-carboxamide (V) and 5-(β-D-ribofuranosyl)-1,3-thiazole-2-carboxamide (XI).

The supernatant fraction of Escherichia coli cells treated with [14C]-2,3-dihydro-1,3-6H-oxazine-2,6-dione ([14C]-3-oxauracil) contains the principal portion of radioactivity in the low molecular weight subfraction. The dominant component of this subfraction is a compound with the properties of 3-oxauridine 5′-monophosphate. The compound is also formed from 3-oxauracil and 5-phosphoribosyl 1-pyrophosphate on incubation with the cell-free extract of E. coli. If this incubation mixture is enriched with adenosine 5′-triphosphate, two further compounds are formed, their properties corresponding to 3-oxauridine 5′-di- and -triphosphates. Treatment of the compound possessing properties of 3-oxauridine 5′-triphosphate with snake venom yielded a non-nucleotide compound with a lower chromatographic mobility than authentic 3-oxauridine. This compound appears to be a ribonucleoside with an open oxazine ring.

2H-1,3-Oxazine-2,6(3H)-dione inhibits the growth of Escherichia coli B, the inhibition being complete at a concentration of 10−4M. It may be relieved with uridine, cytidine and partly with uracil. Orotic acid, cytosine, purine bases and purine ribonucleosides show no effect. At a molar ratio of uridine to the inhibitor of 1:2 the inhibition is completely suppressed. 2H-1,3-Oxazine-2,6(3H)-dione is thus a novel inhibitor of the biosynthesis of pyrimidine precursors of nucleic acids.